JP4874137B2 - Structure of the seal at the nozzle joint in a continuous casting facility for steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure of a nozzle joint part in a continuous steel casting apparatus for preventing the sucking from the joint part between refractory nozzles. <P>SOLUTION: As for the sealing structure of the nozzle joint part in the continuous steel casting apparatus, a hollow disk-like packing material made of a monolithic refractory or flame retardant material is used, two of large and small packing materials are arranged at the inner part and the outer part in the diameter direction on the same flat surface, and molten metal is held in a space formed in the interval with the nozzle joint part. Also, the width in the diameter direction of the metal is defined as &ge;3 mm and the width in the diameter of the packing materials is defined as &ge;10 mm. Alternatively, the thickness of the metal at the room temperature is defined as &ge;0.8 times to &lt;1.3 times of the thickness of the packing material at the room temperature. Alternatively, the width in the diameter direction of the metal is defined as &ge;3 mm and the width in the diameter direction of the packing materials is defined as &ge;10 mm and the thickness of the metal at the room temperature is defined as &ge;0.8 times to &lt;1.3 times of the thickness of the packing material at the room temperature. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a structure of a seal portion of a nozzle joint in a continuous casting facility for steel.

  In the continuous casting of steel, as schematically shown in FIG. 1, molten steel is continuously supplied into the mold by joining a ladle nozzle and a long nozzle, and a tundish lower nozzle and an immersion nozzle, respectively. The joint surfaces are joined using a fireproof packing material. However, since the solids are joined to each other, the problem is a decrease in airtightness due to a minute gap. Further, since molten steel flows inside the nozzle at a high speed, a negative pressure is generated and air is sucked from the nozzle joint surface. For this reason, problems such as product defects due to air bubbles mixed in the products, product defects due to alumina clusters generated by air oxidation, and nozzle clogging have occurred.

  In order to solve the above problem, a technique for improving the airtightness of the nozzle joint has been developed. The high corrosion resistance and airtight packing material disclosed in Patent Document 1 contains a low-melting-point metal in the refractory powder, thereby fixing oxygen mixed from outside air as an oxide and preventing defects due to oxygen mixing. Yes. However, since the fixed oxygen generates an oxide film on the metal surface, there is a problem in that the oxidation reaction rate decreases and the oxygen absorption capacity decreases.

  On the other hand, in the invention disclosed in Patent Document 2, the packing material contains a metal having a high binding force with oxygen and a vapor pressure of 1 atm or higher at the use temperature. In this invention, since the metal vapor is continuously supplied, the stagnation of the reaction for fixing oxygen does not occur.

  However, in any case, oxygen contained by the inhalation of the atmosphere cannot be completely absorbed only by containing a metal as a part of the packing material. Further, since the packing material and the nozzle joint surface are in solid contact, it is impossible to prevent air from being sucked through a minute gap between the solids.

In the invention disclosed in Patent Document 3, the adhesion of the nozzle joint surface is improved by using a packing material that is softened at the operating temperature. However, in normal continuous casting of steel, the nozzle is replaced during casting, but a part of the softened packing material tends to remain on the joint surface of the tundish lower nozzle or the immersion nozzle. For this reason, adhesion of the packing material of the next mounted nozzle is hindered, and the sealing degree is lowered.
Japanese Patent Publication No. 60-15592 JP 2001-105107 A Japanese Patent Laid-Open No. 2003-25060

  An object of the present invention is to stably seal a nozzle joint surface for a long period of time and prevent product defects and operational troubles due to air suction.

  The structure of the seal part of the nozzle joint in the continuous casting equipment for steel according to the present invention made to solve the above problems uses a fire-resistant hollow disc-shaped packing material, and the two large and small packing materials are in the same plane and in the radial direction. The liquid metal is held in a space formed between the nozzle joint surface and the metal, the width in the radial direction of the metal is not less than 3 mm, and the width in the radial direction of the packing material is not less than 10 mm. It is characterized by being. Alternatively, the thickness of the metal at normal temperature is 0.8 times or more and less than 1.3 times the thickness of the packing material at normal temperature. Alternatively, the radial width of the metal is 3 mm or more, the radial width of the packing material is 10 mm or more, and the thickness of the metal at normal temperature is equal to the thickness of the packing material at normal temperature. It is 0.8 times or more and less than 1.3 times.

  In the present invention, since the nozzle joint is sealed with the liquid metal, it is possible to completely prevent the air from being sucked by filling a fine gap formed by joining the solids. In addition, since liquid metal is used, the sealing degree of the joint portion of the nozzle that remains on the joint surface when the nozzle is replaced and is subsequently mounted is not lowered. Therefore, it is possible to prevent product defects and operational troubles due to air suction, which can contribute to the improvement of productivity and quality. Moreover, since it can be operated without the addition of new equipment, the economic effect is great.

  The inventors of the present invention have studied a method for improving the sealing performance of the nozzle joint portion, using a fire-resistant hollow disk-shaped packing material, arranging two large and small packing materials on the same plane in the radial direction, and the nozzle joint surface It has been found that a structure that holds and seals the liquid metal in the space formed between the two is optimal. As a result of various examinations on the dimensions of the structure, the present invention has been achieved based on the obtained knowledge. The width in the radial direction of the metal shown in A of FIG. 2 is preferably 3 mm or more, and the width in the radial direction of the packing material shown in B of FIG. 2 is preferably 10 mm or more. By setting the width of the metal to 3 mm or more, when the packing material is deformed at a high temperature, it is possible to prevent the liquid metal continuous in a circumferential shape from being divided and to stably seal. The metal width is 25 mm or more, and the effect is almost saturated. Further, by setting the width of the packing material to 10 mm or more, it is possible to prevent the molten metal from leaking due to the high temperature deformation of the packing material. The effect is almost saturated when the width of the packing material is 20 mm or more both inside and outside.

  Moreover, it is preferable that the thickness of the metal at room temperature is 0.8 times or more and less than 1.3 times the thickness of the packing material at room temperature. By making the metal thickness at room temperature 0.8 times or more that of the packing material at room temperature, the packing material and the nozzle interface are formed when the packing is compressed vertically during casting. The space can be completely filled with liquid metal, which is preferred. Furthermore, by making the metal thickness less than 1.3 times the thickness of the packing, it is possible to prevent excess liquid metal from entering between the packing material and the nozzle joint surface and reducing the sealing performance.

  Further, it is more preferable when the radial width condition is satisfied and the thickness condition is satisfied.

  In addition, as long as the molten metal in this invention is a metal which is a liquid at the temperature of the nozzle junction part at the time of casting, all can be used conveniently. For example, if the temperature of the nozzle joint during casting is 1200 ° C., Al having a melting point of 661 ° C., Cu having a melting point of 1100 ° C., and the like can be used. In addition, as the refractory packing material in the present invention, any material used as a packing material for a continuous casting nozzle can be suitably used. Examples of commercially available products include the trade name “Kurojog” manufactured by Kurosaki Harima Co., Ltd. and the product name “Seratex” manufactured by Shinagawa Shira brick.

  In addition, the structure of the junction part of this invention is not limited to the junction part between a tundish lower nozzle and a submerged nozzle, but between all the refractories which require airtightness, such as joining between a pan sliding nozzle and a long nozzle. Can be applied to bonding.

In a continuous casting machine for steel composed of a combination of a tundish upper nozzle, sliding nozzle, tundish lower nozzle, and immersion nozzle, operation is performed using the joint between the tundish lower nozzle and immersion nozzle under the conditions shown in Table 1. It was. The casting speed was 1.7m / min, the casting width was 1200mm, the casting thickness was 248mm, and 1350 tons of molten steel was cast. The components of the molten steel are C = 20 ppm, Si = 0.01%, Mn = 0.2%, P = 0.02%, S = 0.01%, Al = 0.015%. In both Examples and Comparative Examples, pure Al was used as the molten metal, and Al ₂ O ₃ —SiO ₂ —C-based refractory powder as the packing material was kneaded and molded using a thermosetting resin.

  In order to evaluate defects caused by atmospheric suction, the slab surface was stepped and the number of bubble defects was counted. The bubble defect here refers to a defect in which bubbles or inclusions are aggregated via bubbles among the defects observed by visual observation. In addition, in order to quantify the amount of oxidation by the sucked air, changes in Al concentration in the molten steel in the tundish delivery side and mold were measured.

  In the example, it was possible to prevent air from being sucked by sealing between the tundish lower nozzle and the immersion nozzle with a liquid. As a result, neither bubble defects nor defects due to alumina clusters occurred. In addition, nozzle clogging did not occur.

  In Comparative Example 1, Al was divided in the circumferential direction by a packing material that had a small metal radial width and was deformed at a high temperature. Further, since the thickness of Al was smaller than that of the packing material, the space formed by the packing material and the nozzle joint surface could not be filled, and the sealing performance was lowered. As a result, suction occurred and bubble defects increased, and oxidation of Al in molten steel also occurred and alumina clusters increased.

  In Comparative Example 2, since the radial width of the packing material was narrow, the outer packing material was cracked, and molten Al leaked to the outside of the nozzle. Moreover, since the thickness of Al was thicker than that of the packing material, a part of the molten Al entered between the packing material and the nozzle joint surface, and the sealing performance was deteriorated. As a result, suction occurred and bubble defects increased on the slab surface. In addition, the oxidation of Al in the molten steel occurred and alumina clusters increased, resulting in nozzle clogging.

It is a schematic diagram of the ladle used for continuous casting, a long nozzle, a tundish, and an immersion nozzle. It is a junction part of the tundish lower nozzle for continuous casting of this invention, and an immersion nozzle, Comprising: It is a longitudinal cross-sectional view of the structure which hold | maintained the liquid metal between the two large and small packing materials.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ladle 2 Upper plate of sliding nozzle 3 Middle plate of sliding nozzle 4 Lower plate of sliding nozzle 5 Long nozzle 6 Tundish 7 Lower nozzle of tundish 8 Immersion nozzle 9 Mold 10a Outer packing material 10b Inner packing material 11 Liquid metal

Claims (3)

  It is a structure of the seal part of the nozzle joint part in the continuous casting equipment of steel, using a fire-resistant hollow disc-like packing material, arranging two large and small packing materials on the inside and outside in the radial direction on the same plane, and with the nozzle joint surface When holding the liquid metal in the space formed therebetween, the width of the metal in the radial direction is 3 mm or more, and the width in the radial direction of the packing material is 10 mm or more. Structure of the seal part of the nozzle joint in the casting facility.     It is a structure of the seal part of the nozzle joint part in the continuous casting equipment of steel, using a fire-resistant hollow disc-like packing material, arranging two large and small packing materials on the inside and outside in the radial direction on the same plane, and with the nozzle joint surface When holding the liquid metal in the space formed between, the thickness of the metal at room temperature is 0.8 times or more and less than 1.3 times the thickness of the packing material at room temperature. The structure of the seal part of the nozzle joint in steel continuous casting equipment.   It is a structure of the seal part of the nozzle joint part in the continuous casting equipment of steel, using a fire-resistant hollow disc-like packing material, arranging two large and small packing materials on the inside and outside in the radial direction on the same plane, and with the nozzle joint surface When holding the liquid metal in the space formed between the metal, the radial width of the metal is 3 mm or more, the radial width of the packing material is 10 mm or more, and the thickness of the metal at room temperature is The structure of the seal part of the nozzle joint in the continuous casting equipment for steel, characterized in that it is 0.8 times or more and less than 1.3 times the thickness of the packing material at normal temperature.

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